Head closure construction for heat exchangers



Feb. 3, 1959 G. D. HAMERSLEY 2,872,065

HEAD CLOSURE CONSTRUCTION FOR HEAT EXCHANGERS Filed Feb. 7, 1956 3Sheets-sheet 1 INVENTOR. Gozdon afiamgns'leg Bygwgg.r

ATTORNEYS Feb. 3, 1959 G. D. HAMERSLEY 2,872,065

HEAD CLOSURE CONSTRUCTION FOR HEAT EXCHANGEIRS Filed Feb. 7, 1956 5Sheets-Sheet 2 69 69 II INVENTOR.

Gordon, D. Hwmersle y BY 9W! 30 30 "30 I ATTORJVEYS Feb. 3, 1959 G. D.HAMERSLEY 2,872,065

HEAD CLOSURE CONSTRUCTION FOR HEAT EXCHANGERS Filed Feb. 7, 1956 3Sheets-Sheet 3 INVENTOR. fiozdoulllz'wmersley BY aw?! ATTORNEYS UnitedStates Patent HEAD CLOSURE CONSTRUCTION FOR HEAT EXCHANGERS ApplicationFebruary 7, 1956, Serial No. 564,016 7 Claims. c1. 220-40 This inventionrelates to a closure construction for the head chamber of a heatexchanger. More particularly, it pertains to a head closure constructionincluding a modified bayonet joint for the closure, particularly adaptedfor use to contain high pressures.

In recent years there has been a trend toward heat exchangers which mustoperate under conditions of higher and higher temperatures andpressures. This trend has created problems in designing the heatexchanger head members with adequate strength to contain the highertemperatures and pressures and without excessive wall thicknesses andmachining costs.

Of course, the head barrel wall and the head cover may be designed tohave increased dimensions. By mak- 'ing thicker head chamber walls ithas been possible to design heat exchangers for operating underincreasing pressures and temperatures.

However, increasing the dimensions of the head chamber creates otherproblems. Where larger volumes are enclosed the thickness of headchamber walls must be increased proportionally. The larger the outsidediameter of the head chamber, the larger the forging cost thereof. Thisincludes not only the cost of added metal involved but also theadditional costs of fabrication. Moreover, the larger the insidediameter the thicker the head barrel wall must be. This in turn involveslarger bending moments to contain the head cover. Accordingly, wherehigher pressures are contemplated, it is desirable to maintain theoutside diameter of the head barrel at a minimum.

The device of the present invention pertains to a modification of atypical heat exchanger construction, such as shown in the Price Pat. No.2,219,659. The Price patent shows lugs or projections extending radiallyinwardly of the barrel wall engaging similar lugs or projectionsextending radially outwardly of the cover plate for the head barrel.With such prior construction it is necessary for the assembly of thecover in the head that the lugs or projections be arranged at spacedintervals equalling the width of the lugs on the cover plate, andvice-versa. The spaces between the lugs are necessary to permitinterfitting during insertion and removal of the head cover. As aresult, when fully assembled the spaces between the lugs in both thehead barrel and the head cover are aligned, thereby not contributing tothe strength of the joint between the cover and the head. For a givenheat exchanger to withstand greater pressures, it is necessary that thelugs must have greater height in order to provide suflicient contact orbearing area between the lugs.

Unfortunately, higher lugs mean a greater gap between the head cover andthe barrel wall. This means that a greater hydrostatic load is createdon the seal between the two members. Further, the higher the lugs thegreater the inside diameter of the barrel at the lugs must be, andtherefore the greater the outside diameter of head. Also, the higher thelugs, the thicker the barrel wall must be to withstand the greaterbending moment about the mean diameter of the wall. The bending momentis a product of the force applied to the lugs and the distance betweenthe lug center line and the mean diameter. Therefore, the bending momentis greater because the higher lugs result in a greater hydrostatic endforce to be carried by the lugs and because the distance is greater witha higher lug.

Furthermore, because of the greater gap between the head cover and thebarrel wall, the size and number of bolts required to contain thehydrostatic pressure creates an additional problem. With the trendtoward higher pressures it becomes more impractical to use bolts forsecuring the head cover to a heat exchanger head, because of theextremely large number and size bolts indicated by calculations using aproper safety factor.

Thus, it is desirable to minimize as much as possible the height orradial thickness of the lugs which will reduce the thickness of thebarrel wall and outside diameter of the head and also reduce the gapbetween the head cover and barrel wall. This is not possible where thetypical heat exchanger construction, such as shown in the Price Pat. No.2,219,659, is used because the total bearing area and circumferentialbearing length and radial bearing width between the lugs isapproximately around the head cover. Since it is necessary to providegaps between the lugs at equally spaced intervals, the total bearingarea of the lug engagement does not exceed 180. For this reason thetypical heat exchanger having the equally spaced lugs around the headcover and barrel wall limits-the extent to which the pressure within theheat exchanger can be increased without entailing the disadvantages ofincreasing the height of the lugs.

I have discovered that a reduction in the height or radial thickness ofthe lugs for a given inside diameter and pressure is possible; This maybe accomplished by providing at least two lugs each on the barrel walland the head cover, the lugs on each member being located in axiallyspaced zones. By reducing the total number of lugs and providing them inequal numbers in spaced axial zones perpendicular to the axis of thehead barrel chamber a lug may be staggered with a lug in another zonethereby providing a bearing area between the engaged surfaces of thelugs at the variou zones extending approximately 360 around the jointbetween the head cover and the barrel wall. Thus, the entire peripheryof the cover at one or another zone or level, throughout 360, isutilized for joint bearing engagement.

In this manner, the total bearing area between the lug's is increased sothat the height of the lugs may be correspondingly reduced. Thus, it ispossible to increase the pressure within a heat exchanger for a givensize of heat exchanger and at the same time reduce the height of thelugs.

Accordingly, it is a general object of the present invention. to providea heat exchanger having overlapping lugs between the head cover and thebarrel wall which lugs have less height than was heretofore requiredfor.

a given size of heat exchanger.

It is another object of this invention toprovide a'joint between thebarrel wall and the head cover having a smaller gap therebetween andtherefore a smaller hydrostatic load on the sealing gasket therebetweenthan heretofore present in a heat exchanger of the same size.

Another object of this invention is to provide a joint between thebarrel wall and the head cover having lugs which require a minimum ofmachining and chipping during fabrication. v

Another object of this invention is to .provide a joint between thebarrel wall and the head cover having a more uniform distribution ofhydrostatic load between the engaged lugs than present in priorstructures.

Another object of this invention is' to provide a barrel "an exchangerhaving a given inside diameter and contained pressure.

Another object of this invention is to provide a barrel wall having anincreased pressure capacity without substantially increasing the amountof metal in the wall.

Another object of this. invention is to provide a joint between a barrelwall and head cover having lugs which 'areapproximately half the size oflugs in height and width as in prior constructions of:the.same capacity.

Still another object of this invention is to provide a head cvoer havinga reduced thickness due to the smaller width of. lugs thereon.v

It .is an object of this invention to provide a joint between a barrelwall and a head cover in which the sizeand number of joint sealing boltsare reduced.

Finally, it is an object of this invention to provide an improved headclosure for a heat exchanger which incorporates the foregoing desideratain an inexpensive manner.

These and other objects and advantages apparent to those skilled in theart from the following description and claims may be obtained, thestated results achieved and the described difiiculties overcome by thediscoveries, principles, apparatus, parts, combinations, subcombinationsand elements which comprise the present invention, the nature of whichis set forth in the following statement, preferred embodiments ofwhichillustrative of the best modes in which applicant has contemplatedapplying the .principlesare set forth in the following description, andwhich are particularly and distinctly pointed out and set forth in theappended claims forming part hereof.

The nature of the improvements in the head closure construction of thepresent invention may be stated in general terms as including in a heatexchanger a barrel wall having an inner surface and terminating in anopen end, apair of locking lugs extending radially inwardly of the innersurface of the barrel wall, the lugs being circumferentially staggeredout of axial alignment and overlap, the lugs being axially spaced by adistance equal to at least the axial width of the lugs, a head closuremember having inner and outer end surfaces, and a pair of locking lugsextending radially outwardly of the outer surface of the head closureand matching the lugs on the barrel wall.

Preferred embodiments of the invention are illustrated, by way ofexample, in the accompanying drawings wherein:

Fig. 1 is a vertical sectional view of the head portion of a heatexchanger provided with the new construction;

Fig. 1a is an enlarged view of a portion of Fig. 1;

Fig. 2 is an end view taken on the line 22 of Fig. 1;

Fig. 2a is an enlarged view of a portion of Fig. 2;

Figs. '3-7 are diagrammatic views showing the successive steps ofassembly of the head closure member within the head member;

Fig. 8 is a diagrammatic end view of the head member showing therelative location of the locking lugs;

Fig. 9 is a vertical sectional view taken on the line '99 of Fig. 8;

Fig. 14 is a diagrammatic end view of head cover for the head barrelshown in Figs. 12 and 13;

Fig. 15 is a side elevational view of the head closure shown in Fig. 14and showing the location of the lugs thereon;

Fig. 16 is a diagrammatic end view, partly in section, of anotherembodiment of the head barrel;

Fig. 17 is a vertical sectional view taken on the line 17-17 of Fig. 16;

Fig. 18 is a diagrammatic end View of the head cover for the head barrelshown in Figs. 16 and 17; and

Fig. 19 is a side elevational view of the head closure shown in Fig. 18and showing the location of locking lugs thereon.

Similar numerals refer to similar parts throughout the various figuresof the drawings.

In Fig. l a portion of a heat exchanger 1 is shown including a shell 2and a head member 3. An annular flange 4, extending outwardly from theouter surface of the shell 2, is provided at one end thereof for thepurpose of attaching the shell to the end of the head member 3 by bolts5. The shell is also provided with a fluid inlet 6 and a fluid outlet 7.

The head member 3 includes a barrel wall 8, forming a head chamber 9. Atube sheet 10 separates the chamber 9 from the shell 2. A plurality orbundle of tubes 11 extend through the shell 2 and have ends secured inand extending through thetube sheet 10 for communication with the headchamber 9. The end of the barrel wall 8 opposite tube sheet 10 isprovided with a removable head cover or closure 12.

The head chamber 9 is divided into an inlet compartment 13 and an outletcompartment 14 by a battle or partition 15 which is welded to oppositesides of the head chamber 9. In addition, an inner cover plate 16extends across the entire head chamber 9 and is secured to the end ofthe baffle or partition 15 by bolts 17. The peripheral portion of thecover plate 16 is secured to an inner shoulder 19 by bolts 18 welded at20 to the barrel wall. The aperture 21 provides for equalizing pressureon opposite sides of the cover plate 16.

As shown in Fig. l the barrel wall 8 is provided with a fluid-inlet 22and a fluid-outlet 23 which are secured in fluid-tight manner by similarwelds 24 and 25.

The head closure or cover 12 is removably secured in place within theopen end of the head member 3 by corresponding interlocking members onthe head barrel and the head closure. The barrel wall 8 is provided witha number of lugs 26 and 27 which extend radially inwardly and axiallyspaced from each other. The lugs 26 and 27 are preferably two in numberbut may be more.

As shown in Figs. 8 and 9, the lugs 26 and 27, being preferably two innumber, extend in approximately segments or a semi-circle, around theinner wall of the head member 3. The lugs 26 and 27 are spaced axiallyof the barrel wall 8, the spacing being equal to at least the width ofsimilar lugs on the head closure member 12. In addition to being axiallyspaced, the lugs 26 and 27 are circumferentially staggered preferably sothat one lug is in axial alignment with the space between the ends ofthe other lug. For example, as shown in Figs. 8 and 9, the lug 26 isaligned with and has approximately the same circumferential length asthe space between the ends of the lug 27, there being no overlapping ofany portions of the lugs 26 and 27. In the same manner, the lug 27 isaxially aligned with the space between the ends of the lug 26. Likewise,the lugs 30 and 31 on the head closure 12 are circumferentiallystaggered to correspond with the positions of the lugs 26 and 27.

As shown in Figs. 1, 2, 1a and 2a, the lug 26 is provided with a cornergroove 28 at the outer end thereof and coextensive therewith. Inaddition, the end face ofthe barrel wall 8 is provided with an annulargasket seal rib 29 engaged by a sealing gasket.

As shown in Figs. 1, and 11; the head closure 12 includes a pair of lugs30 and 31 similar to lugs 26 and 27 on the barrel wall 8. The lugs 30and 31 are preferably two in number and have side surfaces 30a and 31a,respectively, engageable with corresponding side surfaces 26 and 27a onlugs 26 and 27. Thus, as shown in Figs. 10 and 11, the lugs 30 and 31,like the lugs 26 and 27, are substantially semi-circular projections onthe outer surface of the head closure member 12 and are spaced axiallythereof by a distance at least equal to the .width of the lugs 26 and 27on the barrel wall 8.

When the head closure member 12 is completely assembled within thebarrel wall 8 as shown in Fig. 1 there is abutting contact between theengaged lug surfaces extending 360 around the barrel wall, half betweenthe lugs 26 and 30 at the upper segment of the member 12 and halfbetween the lugs 27 and 31 on the lower segment of said member. In thisrespect, the instant construction differs from prior art, such as thatshown in the Price Patent No. 2,219,659, in which only an approximate180 extent of contact can be established between the engaged lugs on thecorresponding barrel wall and head closure.

In addition, the head closure 12 includes a continuous peripheral flange32 which engages the groove 28 in the lug 26 of the barrel wall 8 toprevent the closure 12 from being pushed into the head member 3 too farupon insertion. Further, the flange 32 engages the groove 28 at the sametime that the lug 31 engages a shoulder 3a of the head 3 upon insertionso that the closure 12 is seated in axial alignment with the axis of thehead chamber 9. Furthermore, when the heat exchanger 1 is disposedvertically, rather than on the horizontal axis as shown in Fig. l, theshoulder 3a and the flange 32 prevent the closure member 12 fromdropping from lug-engaging position within the barrel wall 8 uponassembly.

A gasket seal rib 33 is provided on the outer surface of the headclosure 12 and is an annular projection similar to and concentric with,the sealing rib 29 on the barrel wall 8.

As shown in Fig. l, the seal ribs 29 and 33 cooperate to provide afluid-tight seal between the head member 3 and the head closure 12. Anannular gasket 34 is seated on the ribs 29 and 33 and bridges the gaptherebetween. A metal back-up ring 35 covers the gasket 34 and is heldfirmly in place by two clamping rings. One inner clamping ring 36 issecured to the head closure 12 by bolts 38 and an outer clamping ring 37is secured to the end surface of the barrel wall 8 by bolts 39.

The steps by which the head closure 12 is inserted into and removed fromthe head member 3 are shown by the consecutive steps in Figs. 3-7. InFig. 3 the closure 12 is first aligned with the open end of the headmember 3 into which it is then inserted (Fig. 4) until the lugs 30 and31 on the closure 12 contact corresponding lugs 26 and 27 on the headmember 3. The closure 12 is then rotated 180 about its axis until theextremities of the aforesaid abutting lugs are clear of each other (Fig.5) and no longer overlap. The closure 12 may be then further inserteduntil lug 30 thereon contacts lug 27 on the barrel member 3 (Fig. 6).Finally, the closure 12 is rotated again 180 until abutting lugs 26 and30, and 27 and 31 are engaged with each other as shown in Fig. 7.

Manifestly, the closure 12 may be removed from the head member 3 byfollowing the foregoing steps in the reverse order.

In addition to the construction shown in Figs. 1-11 in V which thebarrel wall 8 and the head closure 12 are each provided with two lugs,other modified constructions may be provided as shown in Figs. 12-15 inwhich four lugs are provided and in Figs. 16-19 in which eight lugs areprovided. Thus, the invention is not limited'to a minimtnn number of twolugs, as shown in Figs. 1-11, although two lugs are preferred.

As shown in Figs. 12-15 a barrel wall 40 may be provided with the fourlugs including two lugs 41 and 42 and two lugs 43 and 44, each pair oflugs being disposed in axially spaced zones. Likewise, a head closure 45may be provided with corresponding lugs including a pair of lugs 46 and47 axially spaced from another pair of lugs 48 and 49. The lugs in onezone are staggered or axially aligned with the space between lugs in theother zone. In addition each lug extends over a 90 arc with a space of90 between the ends of the lugs of each pair. The pairs of lugs indifferent zones are staggered so as to cover a complete 360 space aroundand between the barrel wall 40 and the head closure 45.

Hence, upon insertion of the head closure 45 into the barrel wall 40 thelugs of the former may be aligned with the spaces between the lugs ofthe latter for insertion. Thereafter, the head closure 45 may be rotated90 until the space between the lugs of one member is aligned with theother member whereupon the head closure may be then further inserted.Finally, the head closure may again be rotated 90 until correspondinglugs are in abutment with each other so as to provide a 360 contact oflugs around the joint between the barrel wall and the head closure.

Further, a modified construction provides another embodiment in which abarrel wall 50 is provided with eight lugs including pairs of lugs 51and 52, 53 and 54, 55 and 56, and 57 and 58. Each lug extends 90throughout the particular zone in which it is disposed and pairs of lugsare oppositely disposed with spaces equal to approximately 90therebetween. Similarly, a head closure 59 may be provided withcorresponding pairs of lugs 60 and 61, 62 and 63, 64 and 65 and 66 and67. As in the foregoing constructions the lugs ineach zone on the barrelwall 50 and the head closure 59 are circumferentially staggered out ofaxial alignment with the lugs in adjacent zones. Thus, the embodimentshown in Figs. 16-19 includes twice as many lugs as the embodiment shownin Figs. 12-15. The procedure for inserting and removing the headclosure 59 from the barrel wall 50 includes twice as many steps as inthe embodiment of Figs. 12-15. However, inasmuch as twice as many lugsare provided in two additional spaced zones, there are two series of 360contacting or bearing area of lug engagement.

Accordingly, where desired, the number of zones of abutting contact maybe increased in order to obtain 360 or more of contacting or bearingsurfaces between logs of the barrel wall and the head closure.

The number of lugs in a given zone may vary and the number of zones mayvary in accordance with requirements. For example, instead of two lugsbeing provided in two zones in the modified construction shown in Figs.12-15 or two lugs provided in four zones as shown in Figs. 16-19, threelugs may be provided in any zone.

Accordingly, the present invention provides a new head closureconstruction for a heat exchanger by which increased pressures may becontained in the heat exchanger with a given outside diameter of thebarrel Wall. By providing lugs in staggered arrangement and in spacedzones on the closure member and a corresponding number of lugs similarlyarranged on the barrel wall, the total contacting or bearing area of lugengagement between lugs may be extended to occupy substantially 360around the inner surface of the head barrel wall, and such completeperipheral lug engagement may be multiplied at otherspaced axial zoneswhen desired.

Hence, a reduction in the height of all the lugs can be made, therebysubstantially reducing the annular space between the inner surface ofthe barrel Wall and the of the' closure member to form the closure lugs.

barrel wall and closure member.

greatly reduced hydrostatic load upon the seal for the joint betweensaid members.

'- MoreotIenthe reduction in the height of the lugs results in otheradvantages not heretofore obtained. Among these is a reductiori'of thethickness of the head barrel wall due to a reduced bending moment on thewall because (1) the lug center line is closer to the mean diameter'ofthe barrel and (2) the hydrostatic end load carried by the head closuremember is reduced. As a direct result in the reduction in the height ofthe lugs, the inside diameter at the head lugs is substantially reducedand thereby the outside diameter of the head is reduced. I w

A reduction in the diameters and thickness-of the head barrel wallprovides a number of other advantages. First,

the reduced height of the lugs permits a reduction in the width of thelugs which in turn affords a reduction in the total thickness of thehead closure member between the inside and outside surfaces thereof.Second,

the size and number of bolts necessary to provide a fluid seal betweenthe head barrel wall and the closure may be reduced. This, in turn,reduces the time required to assemble or disassemble the heat exchanger.Also machining time, i. e., time required to contour fewer lugs, isreduced. Also, because of the reduced size and number of head bolts, theclamping or hoop rings may be reduced in size.

v.Thelprovision of bearing engagement between the barrel wall andclosure lugs extending throughout the 360 .cbrriplerrintof thetelescoped barrel Wall and closure surfaces achieves other benefits.These members normally are made as forgings with wall thicknesses andsurface configurations arranged so as to permit the blanks to beforged.Metal must in effect be machined, chipped or whittled out to form thelugs on the barrel wall.

Similarly, metal must be removed from the periphery Such machiningoperations necessarily stress the forged metal. Thus, warping due tostress relief is apt to occur.

-Where the lugs extend from 90 to 180 around the inner surface of thebarrel wall substantially less warping will occur thanwhen the lugs arewhittled out as gcar-tooth-like lugs in accordance with prior practice.For example, one or more of the prior art gear-tooth-like lugs may Warpout of position on either or both of the If this occurs it is possiblethat no lug bearing engagement will result at the particular location,thus increasing the load at adjacent engaged lugs.

With the improved construction, such warpage is minimized because of theextended length of the lugs, and the load is therefore more evenlydistributed between the engaged lug surfaces, and is carried throughoutthe entire-360 complement.

The long length lug characteristic of the improved construction providesa certain hoop or ring effect to the lugs which stiffens the same due totheir circumferential extent, so that they resist warpage which mightotherwise tend to occur because of stress relief or for any otherreason.

The 360 load bearing characteristic is sometimes referred to herein assubstantially 360. Obviously it is necessary to provide clearancebetween the ends of lugs at different zones for permitting easyinsertion of the closure member within the barrel member. Such clearanceis indicated at 53 and 69 in Figs. 8 and 10.

The illustration of certain elements in the diagrammatic views of Figs.3 through 19 has been omitted to clearly illustrate generally the modeof assembly of and the cooperative relation between the elements of theimproved closure construction. For instance, no tubereceiving openingsare illustrated in the tube sheet portion of the head member.

The function of the flange 32 in cooperation with the ingthe insertingprocedure has been described. Where thereare only two lugs, .eachextending throughout an approximate arclwithin the barrel wall, theprovision of the shoulder 3a is important. However, where there are twoor more lugs at each Zone, such as the lugs 41 and 42 in Figs. 12 and13, or 51 and 52 in Figs. 16 and 17, relative axial tilting between theclosure and barrel wall while finally seating the. closure is controlledand prevented by the closure flange 32 alone and the barrel wallshoulder 3a is unnecessary, thereby permitting the head chamber diameterto be increased by the elimination of the shoulder 3a and thus space foradditional tubes may be provided without otherwise increasing the sizeof the heat exchanger head construction.

Finally, the many new results obtained by the improved construction haveled to a metal savings alone amounting to hundreds or thousands ofdollars over the cost of metal heretofore required to build an otherwiseequivalent heat exchanger.

In the foregoing description certain terms have been used for brevity,clearness and understanding, but no unnecessary limitations are to beimplied therefrom beyond the requirements of the prior art, because suchwords are used for descriptive purposes herein and are intended to bebroadly construed.

Moreover, the embodiments of the improved construction illustrated anddescribed herein are by way of example, and the scope of the presentinvention is not limited to the exact details of construction shown.

Having now described the features, constructions and principles ofinvention, the characteristics of the improved head closure constructionfor heat exchangers, and the advantageous, new and useful resultsprovided; the new and useful discoveries, principles,-parts, elements,combinations, subcombinations, structures and arrangements, andmechanical equivalents obvious to those skilled in the art, are setforth in the appended claims.

I claim:

1. Head closure construction for heat exchangers, including an annularhead barrel wall having an inner annular surface defining the open endof the head, two closure-engaging lugs projecting radially-inwardly ofthe inner surface of the barrel wall, the lugs being axially spaced andcircumferentially staggered, a closure member within the open end of thebarrel wall, two engaging lugs extending radially-outwardly from theouter surface of the closure member, said closure member lugs beingaxially spaced and circumferentially staggered to match the spacing andstaggering of the barrel wall lugs, the axial spacing between the barrelwall lugs beat least as great as the axial width of the closure lugs,the two closure-engaging lugs projecting inwardly of the inner surfaceof the barrel wall, each extending through a circumferential segment ofsubstantially 180 free of axial overlap so constructed that the extentof circumferential connection of the two axially spaced barrel wall lugswith the barrel wall is approximately 360 around the circumference ofthe inner barrel wall surface.

2. Head closure construction for heat exchangers, including an annularhead barrel wall having an inner annular surface defining the open endof the head, four closure-engaging lugs projecting radially-inwardly ofthe inner surface of the barrel wall, the lugs being axially spaced andcircumferentially staggered, a closure member within the open end of thebarrel wall, four engaging lugs extending radiallyoutwardly from theouter surface of the closure member, said closure member lugs beingaxially spaced and circumferentially staggered to match the spacing andstaggering of the barrel wall lugs, the axial spacing between the barrelwall lugs being at least as great as the axial width of the closurelugs, the four closure-engaging lugs projecting inwardly of the innersurface of the barrel wall, each extending through a circumferentialsegment of substantially 90 free of axial overlap so constructed thatthe extent of circumferential connection of the four axially spacedbarrel wall lugs with the barrel Wall is approximately 360 around thecircumference of the inner barrel wall surface.

3. Head closure construction for heat exchangers, including an annularhead barrel wall member having an inner annular surface defining theopen end of the head, at least two closure-engaging lugs projectingradially-inwardly of the inner surface of the barrel wall, the lugsbeing axially spaced and circumferentially staggered, onecircumferential end of one of the lugs being substantially in axialalignment with the opposite circumferential end of an adjacent axiallyspaced lug, the other end of said one lug being substantially in axialalignment with the opposite circumferential end of an adjacent axiallyspaced lug, said axially spaced and circumferentially staggered lugshaving connection with the barrel wall for approximately 360 around thecircumference of the inner surface of the barrel Wall, a closure memberwithin the open end of the barrel wall, at least two engaging lugsextending radially outwardly from the outer surface of the closuremember, said closure member lugs being axially spaced andcircumferentially staggered to match the spacing and staggering of thebarrel wall lugs, and the axial spacing between the barrel wall lugsbeing at least as great as the axial width of the closure lugs.

4. Head closure construction for heat exchangers as defined in claim 3,in which the closure member is telescopically and rotatably positionedWithin the barrel wall member to establish lug engagement, and in whichmeans is provided extending continuously circumferentially around one ofthe barrel wall and closure members engageable with the other member toprevent overinsertion of the closure member Within the barrel wallmember.

5. Head closure construction for heat exchangers as defined in claim 4,in which the continuously extending means includes a continuouslyextending outwardlyprojecting flange at the outer end of the closuremember engageable with one of the barrel wall member lugs.

6. Head closure construction for heat exchangers as defined in claim 4,in which the continuously extending means includes an annular flangeprojecting from the closure member engageable with a barrel wall memberlug, and an annular barrel wall member shoulder engageable with theclosure member lug.

7. Head closure construction for heat exchangers, in cluding an annularhead barrel wall member having an inner annular surface defining theopen end of the head, closure-engaging means projectingradially-inwardly of the inner surface of the barrel wall, theclosure-engaging means including lug means located at axially spacedZones, the lug means at one Zone being out of axial alignment with andextending substantially throughout the circumferential space between theends of the lug means located at the second axially spaced zone, eachcircumferential end of any lug means at one zone being substantially inaxial alignment with the opposite circumferential end of an adjacentaxially spaced lug means located at the second zone whereby the lugmeans at said two zones have connection with the barrel wall forapproximately 360 around the circumference of the inner surface of thebarrel wall, a closure member within the open end of the barrel wall,engaging means extending radially-outwardly from the outer surface ofthe closure member, said engaging means on the closure member comprisinglug means located at axially spaced zones and matching the spacing ofthe barrel wall lug means, and the axial spacing between the barrel walllug means at said two zones being at least as great as the axial widthof the closure member lug means.

References Qited in the file of this patent UNITED STATES PATENTS837,648 Strom et al. Dec. 4, 1906 2,342,186 Fischer Feb. 22, 19442,473,555 Weiss June 21, 1949 2,652,170 Lotter et al. Sept. 15, 1953

